/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.apache.tomcat.util.collections;

import java.util.Enumeration;

/**
 * Enumerate the distinct header names. Each nextElement() is O(n) ( a
 * comparation is done with all previous elements ).
 * 
 * This is less frequesnt than add() - we want to keep add O(1).
 */
public final class MultiMapNamesEnumeration implements Enumeration {
	int pos;
	int size;
	String next;
	MultiMap headers;

	// toString and unique options are not implemented -
	// we allways to toString and unique.

	/**
	 * Create a new multi-map enumeration.
	 * 
	 * @param headers
	 *            the collection to enumerate
	 * @param toString
	 *            convert each name to string
	 * @param unique
	 *            return only unique names
	 */
	MultiMapNamesEnumeration(MultiMap headers, boolean toString, boolean unique) {
		this.headers = headers;
		pos = 0;
		size = headers.size();
		findNext();
	}

	private void findNext() {
		next = null;
		for (; pos < size; pos++) {
			next = headers.getName(pos).toString();
			for (int j = 0; j < pos; j++) {
				if (headers.getName(j).equalsIgnoreCase(next)) {
					// duplicate.
					next = null;
					break;
				}
			}
			if (next != null) {
				// it's not a duplicate
				break;
			}
		}
		// next time findNext is called it will try the
		// next element
		pos++;
	}

	public boolean hasMoreElements() {
		return next != null;
	}

	public Object nextElement() {
		String current = next;
		findNext();
		return current;
	}
}
